1. Field of the Invention
The present invention relates to a satellite signal receiving antenna unit for receiving radio waves from an earth satellite, and particularly to a satellite signal receiving antenna unit for receiving radio waves circularly polarized such as satellite radio broadcasting.
2. Description of the Related Art
The satellite signal receiving antenna unit is set on a moving machine such as an automobile or a ship. A GPS antenna unit which, upon reception of a signal of gigahertz band transmitted from a satellite, detects the latitude and longitude thereby to obtain the present position data, and a satellite radio receiving antenna unit which receives radio broadcasting has been known as the satellite signal receiving antenna units. The satellite signal receiving antenna unit is combined with a reception unit and a signal processing unit.
In the satellite broadcasting receiving antenna unit, an antenna body is generally housed in a resin-made case, and a coaxial cable connected to the antenna body is led from the case and connected to a reception unit. The antenna unit comprises members such as an antenna body and a shield case. The antenna body comprises an antenna element, and an antenna substrate on which antenna circuit parts such as an amplifier are mounted and the predetermined circuit patterns such as a power supply pattern and a ground pattern are formed. The shield case is attached to this antenna substrate so as to cover the mounted circuit parts, thereby performing as an electromagnetic shield.
Since the satellite signal receiving antenna unit is set to the moving machine such as the automobile to be used, the coaxial cable is firmly fixed onto the antenna substrate to hold vibration-resistance and shock-resistance. Therefore, on the side surface of the shield case from which the coaxial cable is led, a cable holding part is formed integrally, and when the shield case is attached to the antenna substrate, the cable holding part presses the coaxial cable on the antenna substrate, whereby shielding of the mounted circuit parts and holding of the coaxial cable are performed. (For example, JP-UM-A-7-42524 or JP-A-2003-17154)
In the above conventional satellite signal receiving antenna unit, the cable holding part is formed on the side surface of the shield case from which the coaxial cable is led. In a case where the coaxial cable is soldered to each connection pattern formed in the inner position of the antenna substrate which is distant from the holding position by the cable holding portion, soldering is performed in a state where a lead wire of the coaxial cable comes up from the connection pattern. That is, aerial soldering is performed, so that it becomes difficult to perform the connection with enough strength.
Therefore, since it is necessary to perform soldering while the lead wire of the coaxial cable is being pressed on the connection pattern of the antenna substrate by use of an appropriate jig, working performance becomes a problem. Further, since stress is concentrated on the soldering portion, peeling-off of solder is also produced thereby to cause a problem that reliability lowers the solder can peel off, thereby decreasing reliability.
For example, in order to prevent aerial soldering, it is thought that the connection pattern of the antenna substrate is formed in the vicinity of the lead part of the coaxial cable thereby to bring the soldering part close to the holding position by the cable holding portion. However, since freedom in pattern formation and mounting of parts on the antenna substrate is limited, it is difficult to realize size-reduction and improvement of assembly performance.